Abstract
Nitrogen is an essential nutrient for yeasts and its relative abundance is an important modulator of fermentation kinetics. The main sources of nitrogen in food are ammonium and free amino acids, however, secondary sources such as oligopeptides are also important contributors to the nitrogen supply. In yeast, oligopeptide uptake is driven by different families of proton–coupled transporters whose specificity depends on peptide length. Proton-dependent Oligopeptide Transporters (POT) are specific to di- and tri-peptides, whereas the Oligopeptide Transport (OPT) family members import tetra- and pentapeptides. Recently, the novel family of Fungal Oligopeptide Transporters (FOT) has been identified in Saccharomyces cerevisiae wine strains as a result of a horizontal gene transfer from Torulaspora microellipsoides. In natural grape must fermentations with S. cerevisiae, Fots have a broader range of oligopeptide utilization in comparison with non-Fot strains, leading to higher biomass production and better fermentation efficiency. In this review we present the current knowledge on the diversity of oligopeptide transporters in yeast, also discussing how the consumption of oligopeptides provides an adaptive advantage to yeasts within the wine environment.
Highlights
Yeasts are unicellular, eukaryotic organisms that are commonly found in food environments, where they normally consume sugars to produce energy in anaerobic conditions
Experiments on synthetic media containing ammonia and free amino acids supplemented with yeast hydrolysate have shown that nitrogen provided by peptides eventually constitutes 40% of the yeast protein fraction during alcoholic fermentation, which highlights the important anabolic role of oligopeptides versus other nitrogen sources such as ammonium, which only contributes 20% of this fraction (Kevvai et al, 2016)
Peptide transport in yeast cells greatly depends on the transport system and environmental factors, specially the presence of other nitrogen sources such as ammonium or amino acids (Figure 1)
Summary
Eukaryotic organisms that are commonly found in food environments, where they normally consume sugars to produce energy in anaerobic conditions. Oligopeptides assimilation can lead to the release of some amino acids that are consumed after depletion of the other nitrogen sources (Marsit et al, 2016).
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